1. Field of the Invention
This invention relates generally to die sets for use in presses, and more particularly to guide posts and bushings for die sets.
2. Description of the Prior Art
Prior art die sets typically include an upper and lower die shoe. One or the other of the die shoes has a set of posts (usually four) affixed to it, and the die shoe has a set of bushings affixed to it. The bushings are received on the posts and serve to guide the shoes as they are brought together during press operation for the forming or punching of a part. It is essential that accuracy be maintained in guiding the die shoes, so that the mating parts of the dies secured thereto cooperate as intended. Otherwise early damage and destruction of the dies, and possibly also the press itself, may result.
After extended periods of use, guide posts and bushings of die sets become worn. As the wear increases, the possibility of misalignment of the die parts increases with the attendant possibility of damage to the dies themselves. Therefore it becomes necessary to repair or replace the posts or bushings. This usually requires removal from the die shoes, with the result that the die set is inoperative for whatever period is required in this procedure. Then, upon replacement of the posts and bushings, considerable time is required to again provide perfect alignment of the dies mounted in the die shoes.
Prior art patents noted in the course of a search for the subject invention are as follows:
U.S. Pat. No. 2,177,958--Link PA1 U.S. Pat. No. 2,316,468--Thomas PA1 U.S. Pat. No. 2,420,296--Bishop et al. PA1 U.S. Pat. No. 2,774,430--Blazek PA1 U.S. Pat. No. 3,092,425--Conner PA1 U.S. Pat. No. 3,273,944--Hammon PA1 U.S. Pat. No. 3,353,876--Moyer
Of these patents, the Conner, Moyer, and Blazek patents disclose anti-friction bearings in die sets. The Hammon patent shows a die set having aluminum oxide bearing surfaces. The Link, Thomas and Bishop patents show replaceable sleeves. None of these references shows post bearing sleeves and bushing inserts which are readily removable without disturbing the posts or bushings for replacements in die sets.